I'm the developer of GameRanger, a PC/Mac multiplayer online gaming service supporting over 600 games that has been running since 1999. Not very well known due to being Mac-only until late 2008, but just hit 5 million registered members last month mostly from word of mouth. Many of these games are ex-GameSpy or already had their existing services shut down long ago.

I've been trying to reach out to any affected developers and publishers, as I'm well-positioned to be able to help out. My only interest is in keeping these games alive, no matter how small the player base is. I'm not sure if I can help with the console games; that may depend on Glu (I've reached out to them as well).

Let's talk about some old games. Take, for one, Halo 2. It's now going to be permanently offline, as a result of it being connected to Microsoft's services. Let's go back though. Take a look at Jedi Knight. Can you play that online anymore? Nope. Microsoft service. Dead. Any of those other MSN/"Zone" games? Dead. At least DirectPlay supported LAN in the same manner as online, so the games all still support that.

You raise a valid point, though Jedi Knight: Dark Forces II and nearly all of the MSN Zone games can still be played online through GameRanger (see the list). You'd be amazed at how many games of Age of Empires II are being played each day -- it puts many recent games to shame.